I would act with care. Historically a pilot could receive limited instruction on their non UK aeroplane but not instruction for the gaining of a licence or rating. The reason for this was the restrictions that limited hire and reward for a non UK, and once upon a time non EASA, aircraft and which was not part not part of an AOC valid for UK airspace. Anything to do with EASA is in a state of uncertainty as the CAA make their way through the mountain of rule making and all the ifs and buts required since December 31st.
The CAA will be hopeless on this and will take months to respond if they do. The best course of action is to contact the Department of Transport who will make the decision anyway.